Mediation of ocular tetrahydrocannabinol effects by adrenergic nervous system

Abstract

Intravenously administered Δ 9-tetrahydrocannabinol (THC) lowers the intraocular pressure by 25% and increases total outflow facility ( C tot) by 25% of a normal rabbit eye. Different effects on these parameters are seen in the animal which has been treated with a ganglionic blocking agent or the eye subjected to unilateral superior cervical ganglionectomy. The intraocular pressure fall, and rise of C tot are substantially reduced to about 30 or 40% of the normal THC-induced change following unilateral ganglionectomy despite a normal response in the contralteral eye. Intravenous hexamethonium chloride, a ganglionic blocking agent, causes a substantial reduction in the intraocular pressure effect of THC with little effect on the outflow facility response to THC. The ocular effects of tetrahydrocannabinol are mediated through the adrenergic innervation system, with peripheral sympathomimetic activity as well as a primary effect exerted through the central nervous system. The latter pathway is of major importance for the full development of the normal Δ 9-tetrahydrocannabinol effect.